1. Field of the Invention
The present invention relates to a heat ray screening glass which has a high visible light transmittance and a low visible light reflectivity and is capable of screening a part of the solar radiation energy. It is particularly suitable for use as automotive window glass and building glazing.
2. Description of the Prior Art
Among the known glasses having a high visible light transmittance and is capable of screening a part of the solar radiation energy, is one which is composed of a glass substrate, a layer of oxide having a high refractive index, a layer of metal nitride, and a layer of oxide having a high refractive index. These layers are laminated on the glass substrate. (See SPIE. vol. 324 (1982) 52.) There is known a heat ray screening glass in which the oxide having a high refractive index consists of chemically stable TiO.sub.2 or SnO.sub.2 and the metal nitride consists of chemically stable nitride of Ti, Zr, or Hf which belong to Group IVa of the Periodic Table. It has good durability and can be used alone as a single plate.
The conventional heat ray screening glass has a disadvantage that when a light is transmitted through and reflected on the conventional glass it produces strong interference colors (red, reddish purple, yellow, etc.) because of the interference between the laminated layers and a visible light. These interference colors make the glass look to be different from the glass itself and hence are undesirable from the standpoint of design when the glass is used for automotive windows. The heat ray screening glass for automotive windows should be able to reduce the amount of direct sunlight entering the automotive room, thereby making the driver and passengers feel comfortable. From the standpoint of design, it is strongly required to keep the own color of the glass.